Peel bond strength between 3D printing tray materials and elastomeric impression/adhesive systems: A laboratory study.

OBJECTIVES: The present study aimed to evaluate the bonding between three 3D printed custom tray materials and three elastomeric impression/adhesive systems using the peel test. METHODS: Test blocks were 3D printed by three different technologies using Dental LT, FREEPRINT tray, and polylactide (PLA) tray materials. The reference test blocks were conventionally fabricated with Zeta Tray LC, a light-curing resin. The surface topographies of the four tray materials were investigated by scanning electron microscopy (SEM) analyses and roughness measurements. The peel bond strength between the four tray materials and three impression/adhesive systems, vinylsiloxanether (VSXE), vinyl polysiloxane (VPS), and polyether (PE), was measured (n=12 per group). The peeling failure modes and rupture sites were identified microscopically. RESULTS: The four tray materials featured different surface topographies. The peel bond strength was not significantly different with VSXE and PE, but PLA and the reference showed higher peel bond strength with VPS than the Dental LT and FREEPRINT tray (p<0.05). The rupture site of adhesive failure in all groups was partly at the adhesive-impression material interface and partly within the adhesive but never at the adhesive-tray material interface. SIGNIFICANCE: The 3D printed tray materials can achieve satisfactory chemical compatibility with the adhesives of VSXE, VPS, and PE. Surface topographies generated by the 3D printing technologies may affect bonding. Generally, 3D printed tray materials can provide clinically adequate bond strength with the elastomeric impression/adhesive systems. PLA is recommended for bonding with VPS when severe impression removal resistance is detected.

Implementing healthier foodservice guidelines in hospital and federal worksite cafeterias: barriers, facilitators and keys to success.

BACKGROUND: Healthy foodservice guidelines are being implemented in worksites and healthcare facilities to increase access to healthy foods by employees and public populations. However, little is known about the barriers to and facilitators of implementation. The present study aimed to examine barriers to and facilitators of implementation of healthy foodservice guidelines in federal worksite and hospital cafeterias. METHODS: Using a mixed-methods approach, including a quantitative survey followed by a qualitative, in-depth interview, we examined: (i) barriers to and facilitators of implementation; (ii) behavioural design strategies used to promote healthier foods and beverages; and (iii) how implementation of healthy foodservice guidelines influenced costs and profitability. We used a purposive sample of five hospital and four federal worksite foodservice operators who recently implemented one of two foodservice guidelines: the United States Department of Health and Human Services/General Services Administration Health and Sustainability Guidelines ('Guidelines') in federal worksites or the Partnership for a Healthier America Hospital Healthier Food Initiative ('Initiative') in hospitals. Descriptive statistics were used to analyse quantitative survey data. Qualitative data were analysed using a deductive approach. RESULTS: Implementation facilitators included leadership support, adequate vendor selections and having dietitians assist with implementation. Implementation barriers included inadequate selections from vendors, customer complaints and additional expertise required for menu labelling. Behavioural design strategies used most frequently included icons denoting healthier options, marketing using social media and placement of healthier options in prime locations. CONCLUSIONS: Lessons learned can guide subsequent steps for future healthy foodservice guideline implementation in similar settings.

Comparison of different in vitro tests for biocompatibility screening of Mg alloys.

Standard cell culture tests according to ISO 10993 have only limited value for the biocompatibility screening of degradable biomaterials such as Mg alloys. The correlation between in vitro and in vivo results is poor. Standard cytotoxicity tests mimic the clinical situation to only a limited extent, since in vivo proteins and macromolecules in the blood and interstitial liquid will influence the corrosion behaviour and, hence, biocompatibility of Mg alloys to a significant extent. We therefore developed a modified cytotoxicity test simulating the in vivo conditions by use of bovine serum as the extraction vehicle instead of the cell culture medium routinely used in standard cytotoxicity testing according to ISO 10993-5. The modified extraction test was applied to eight experimental Mg alloys. Cytotoxicity was assayed by inhibition of cell metabolic activity (XTT test). When extraction of the alloy samples was performed in serum instead of cell culture medium the metabolic activity was significantly less inhibited for six of the eight alloys. The reduction in apparent cytotoxicity under serum extraction conditions was most pronounced for MgZn1 (109% relative metabolic activity with serum extracts vs. 26% in Dulbecco's modified Eagle's medium (DMEM)), for MgY4 (103% in serum vs. 32% in DMEM) and for MgAl3Zn1 (84% vs. 17%), resulting in a completely different cytotoxicity ranking of the tested materials when serum extraction was used. We suppose that this test system has the potential to enhance the predictability of in vivo corrosion behaviour and biocompatibility of Mg-based materials for biodegradable medical devices.

[The effect of the aeration status on the corrosion behavior of Ni-Cr alloys]. / Einfluss der Belüftungssituation auf das Korrosionsverhalten von Ni-Cr-Legierungen.

Using in vitro tests, the influence of aeration cells that develop in narrow crevices of dental restorations, on the corrosion behaviour of two Ni-Cr alloys (Wiron 88 and Rexillium III) was investigated. The results revealed a 1.6-fold higher ion release in the deaerated part of the electrolyte compared with the aerated one, whereas the ion release was 18-fold higher with Rexillium III. The total analyzed substance loss was 11.1 (S.D. 5.7) and 181.9 (S.D. 48.0) micrograms/cm2, respectively.